1. Field of the Invention
The present invention relates to an image forming apparatus, an image forming method, and printed matter.
2. Description of the Related Art
Inkjet recording apparatuses are known that discharge ink droplets from heads having nozzle orifices to record images on sheets. The inkjet recording apparatuses have been recently progressively downsized and reduced in cost. On the other hand, the inkjet recording apparatuses are also required to provide higher image quality. The inkjet recording apparatuses are required to provide higher image quality by increasing recording density in a main-scanning direction, for example.
For example, Japanese Laid-open Patent Publication No. 2004-209765 discloses an image forming apparatus that has a plurality of kinds of masks that define dot arrangement with recording density of printing image data or more and performs recording with density of the printing image data or more while referring to a randomly selected mask. The image forming apparatus disclosed in Japanese Laid-open Patent Publication No. 2004-209765 further discloses a technique that varies the position of the mask referred to by color, thereby shifting a dot arrangement position by color and enabling a record with main-scanning resolution up to four times higher than that of the printing image data.
In order to increase the recording density in the main-scanning direction in the inkjet recording apparatuses, it is required to improve the accuracy of a linear encoder for detecting the position of a head in the main-scanning direction. However, when the accuracy of the linear encoder is improved in the inkjet recording apparatuses, the linear encoder increases in processing cost or the like, leading to an increased cost as a whole.
In view of the above-described conventional problems, there is a need to provide an image forming apparatus having improved recording density in the main scanning direction at low cost, an image forming method, and print matter.